Class 7 Exam  >  Class 7 Notes  >  Social Studies (SST) Class 7  >  Important Questions: Inside Our Earth

Important Questions: Inside Our Earth | Social Studies (SST) Class 7 PDF Download

Q1: How are minerals useful to mankind?
Ans: Minerals are useful to humankind in the following ways:

  • Some are used as fuels. For example, coal, natural gas and petroleum.
  • They are also used in industries – iron, aluminium, gold, uranium, etc, in medicine, in fertilisers, etc.


Q2: What are the uses of rocks?
Ans: Uses of rocks

  • The hard rocks are used for making roads, houses and buildings.
  • Stones are used in many games. For example, seven stones (pitthoo), hopscotch (stapu/kit kit), five stones (gitti).


Q3: How are extrusive and intrusive rocks formed?
Ans:

  • Extrusive rock: When molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine grained structure.
  • Intrusive rocks: Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous.


Q4: Sedimentary rocks are formed from sediments. Give reason.
Ans: Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.

Q5: What do you know about earth’s interior?
Ans: The earth is made up of several concentric layers with one inside another.

  • Crust: The uppermost layer over the earth’s surface is called the crust. It is the thinnest of all the layers. It is about 35 km. on the continental masses and only 5 km. on the ocean floors.
  • Mantle: Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
  • Core: The innermost layer is the core with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife. The central core has very high temperature and pressure.


Q6: Write a note on various types of rocks?
Ans: There are three major types of rocks: igneous rocks, sedimentary rocks and metamorphic rocks.

  • Igneous rocks: When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks. They are also called primary rocks. There are two types of igneous rocks: intrusive rocks and extrusive rocks.
    • Extrusive igneous rocks: When molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. For example, basalt.
    • Intrusive igneous rocks: Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks. Granite is an example of such a rock.
  • Sedimentary rocks: Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments. These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks. For example, sandstone is made from grains of sand.
  • Metamorphic rocks: Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure. For example, clay changes into slate and limestone into marble.

Q7: Describe the different layers of the earth.
Ans: The earth is made up of three concentric layers with one inside another—crust, mantle and core.
  • Crust: It is the uppermost solid layer of the earth. It is the thinnest of all the layers. It is about 35 km on the continental masses and only 5 km on the ocean floor.
  • Mantle: Below the crust of the earth lies a very thick layer called the mantle. It extends up to a depth of 2900 km below the crust. The main elements of this layer are silicon and magnesium and is called sima.
  • Core: It is the innermost layer with a radius of about 3500 km. It is mainly made up of nickel and iron and is called nife. The central core has very high temperature and pressure.

Q8: How are extrusive and intrusive rocks formed?
Ans: 
Intrusive and extrusive rocks are types of igneous rocks which are formed when magma cools down and solidifies.
  • Extrusive rocks: When the molten magma comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks. They have a very fine structure. For example, basalt.
  • Intrusive rocks: Sometimes the molten magma cools down deep inside the earth’s crust or surface. Solid rocks so formed are called intrusive igneous rocks. Since they cool down slowly, they form large grains. For example, granite.

Q9: What are metamorphic rocks?
Ans:
 Metamorphic rocks are actually igneous or sedimentary rocks which changed due to great heat and pressure. Small crystals combine together to form large crystals. The act of metamorphism takes hundreds of years. Examples—clay changes into slate and limestone changes into marble.

Q10: What is mantle?
Ans:
 It is an intermediate layer lies between the crust and the core of the earth .Its avg thickness is about 29,00 km. It is believed to consist of solid ultra basic rocks, rich in iron and magnesium.

Q11: What is the importance of outer crust to us?
Ans: The solidified outer crust of the earth is of great importance to us .This thin crust just like the skin of an apple, forms the stage on which human life and civilization have developed. It has the valuable soil and gives us most of our minerals.

Q12: What is the source of knowing of the layered structure of the earth?
Ans: The layered structure of the earth has been known on the basis of variation in temperature, pressure and the density of the material in the interior. The behaviour in the earth quake shock waves travelling from the centre of their origin in all directions has been much helpful to this end.

Q13: Give example of all the three major forms of rocks?
Ans:
  • Igneous-granite, basalt
  • Metamorphic rocks- marble, slate, graphite
  • Sedimentary- limestone, sandstone.

Q14: What are the uses of rocks?
Ans: Rocks are very useful to man, used for making roads, houses and building. Rocks are the source of precious metals like gold, silver, and platinum. We use stone in many games. For example, seven stone, top scotch.

Q15: Distinguish between crust and core.
Ans:
  • Crust is the uppermost solid layer of the earth while core is the innermost layer.
  • Crust is the thinnest of all the layers. It is about 35 km thick.
  • The main elements of the crust are silicon, aluminium and magnesium while the main elements of the core are nickel and iron.
The document Important Questions: Inside Our Earth | Social Studies (SST) Class 7 is a part of the Class 7 Course Social Studies (SST) Class 7.
All you need of Class 7 at this link: Class 7
65 videos|328 docs|46 tests

Up next

65 videos|328 docs|46 tests
Download as PDF

Up next

Explore Courses for Class 7 exam
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Download the FREE EduRev App
Track your progress, build streaks, highlight & save important lessons and more!
Related Searches

Objective type Questions

,

MCQs

,

Free

,

ppt

,

Viva Questions

,

pdf

,

practice quizzes

,

Important Questions: Inside Our Earth | Social Studies (SST) Class 7

,

Important questions

,

video lectures

,

Summary

,

study material

,

Previous Year Questions with Solutions

,

Extra Questions

,

Exam

,

Important Questions: Inside Our Earth | Social Studies (SST) Class 7

,

Semester Notes

,

mock tests for examination

,

Important Questions: Inside Our Earth | Social Studies (SST) Class 7

,

past year papers

,

Sample Paper

,

shortcuts and tricks

;